The present disclosure relates generally to medical devices, and particularly, to intraluminal support frames or stents for implantation within a human or animal body for repair of damaged vessels, ducts, or other physiological pathways.
Various types of disease conditions present clinical situations in which a vessel of a patient needs to be artificially supported to maintain an open passageway through which fluids, such as blood, can flow. For example, blood flow through an artery can be impeded due to a build-up of cholesterol on the interior wall of the vessel. Also, vessel walls can be weakened be a variety of conditions, such as aneurysms.
Intraluminal support frames, sometimes referred to as stents, provide an artificial mechanism to support a body vessel. Stents are typically tubular-shaped members that are placed in the lumen of the vessel and, once deployed, exert a radially-outward directed force onto the vessel wall to provide the desired support.
Stents are typically positioned at the point of treatment or target site by navigation through the vessel, and possibly other connected vessels, until the point of treatment is reached. This navigation may require the stent to be able to move axially through the vessel(s) prior to deployment, while still maintaining the ability to exert an outward force on the interior wall once deployed. Accordingly, stents typically have radially unexpanded and expanded configurations. In the unexpanded configuration, the stent has a relatively small diameter that allows it to move axially through the vessel. In the expanded configuration, the stent has a relatively large diameter that allows it to exert an outward force on the interior wall of the lumen, thereby providing the desired support to the vessel.
Stents are typically either self-expanding stents or balloon expandable stents, which categorizes how the stents move from the radially unexpanded configuration to the expanded configuration. Balloon expandable stents typically provide greater radial force and circumferential compression resistance over self-expanding stents. However, balloon expandable stents generally are stiffer structures. Their inflexibility and lack of elasticity limit their longitudinal flexibility and ability to conform to tortuous vessels, such as the superficial femoral artery (SFA), and can lead to permanent deformation when subjected to high levels of motion. For example, certain vessels, such as the SFA, provide a high-level motion environment that contributes to greater bending and longitudinal compression loads to stent structures than vessels positioned in less motion environments. Thus, the use of self-expanding stents in this environment is typically more attractive as balloon expandable stents may be prone to experience permanent deformation in such environment, unless the stent architecture of balloon expandable stents can be improved for such environment.